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data on this point we are obliged to resort to another line of observations to determine this matter.

It has been shown by many experiments that when the cadaver is stood erect and the legs and ankles are fixed (to pre,ent the cadaver from collapsing on the ground), the trunk falls forward from the hips. In the erect position then the trunk is held extended on the legs by the combined and continued action of the posterior musculature, the chief factors here being the hamstrings, the glutei and the erector spinal muscles.

If, however, for any reason the center of gravity becomes displaced forward, the strain on the posterior musculature necessarily becomes increased throughout, because the vertical stress at each level is determined by the horizontal distance of that point from a perpendicu­lar dropped from the center of gravity, and, if this moves forward, the strain increases in proportion to the increased horizontal distances. So, too, other things being equal, the points farthest away from this perpen­dicular suffer the greatest stress.

Having presented these preliminary considerations in mechanics, we come next to the report of our experi­mental observations on the disturbances of balance.

Throughout our remarks on this subject, we desire that it should be remembered that our experimental studies were concerned only with balance and the modifi­cations produced on balance by corsets and high-heeled shoes, and that the other effects of these are not dis­cussed.

In our experimental work it early became apparent that the assumption of any enforced position for even the short time involved in an observation left behind it an alteration of the normal, or unrestrained position which persisted for a number of minutes; also that mere maintenance of the standing position resulted in the appearance, after a surprisingly short but variable time, of a modification of the normal which we designated as a "fatigue position."

For these reasons it was necessary in our corset work to take a fresh observation of the normal attitude before each corset observation, to insist that each corset observa­tion should be followed by at least fifteen minutes' com­plete muscular relaxation in a recumbent posture, and to limit the number of corset observations in any one sit­ting to two at most.

In their effects on the antero-posterior position of the body, corsets may he divided into three classes and each class must be studied separately if clear results are to be obtained. After much unsuccessful search for a satis­factory nomenclature for these three classes we have adopted the brief and comprehensible, though somewhat unscientific terms: the neutral, the bad, and the good corset.

The indifferent or neutral class includes the great majority of all corsets worn by women, but it must be remembered of this statement that it applies only to the effects of corsets on balance, posture and static backache. Many of the posturally indifferent corsets may be harm­ful in other ways. Few of them are beneficial. At the present time practically all ready-made corsets belong to the posturally indifferent class. Indeed, we found it necessary to have good and bad corsets specially made for each of the models with whom we experimented. Until we did this, our results were confusing, but after this precaution was taken the results of observations on

all forms of corset became uniform, consistent. and sufficlently evident to permit of clear record and definite deductions, Neutral corsets produced no appreciable effect on body balance.

We use the term "bad corset" to designate that whole class of corsets the use of which we have learned to asso­ciate clinically, and to some extent experimentally, with the existence and production of static backache. All corsets of this class have definite common characteristics. All produce the same effect on posture when submitted to exact observation, varying only in the degree of their results. All tend to increase or produce static backache if persistently worn.

The common characteristics of this class of (bad) corsets are as follows: 1. They are long behind (especially at the top) and short in front (especially at the bottom) 2. They are cut to exert their greatest pressure at the waist and at the top and bottom are capable of exerting pressure only against the wearer's back. 3. They have strongly marked sacral curves, but are otherwise straight in the back, and are highly incurved at the waist in front.

Figure 3 is an outline of a representative specimen of the bad corset made. from life by a very competent artist. The bad corsets uniformly moved the center of gravity back and effected an Important alteration of posture. To the unaided eye this usually appeared as a simple movement of the shoulders forward, but this effect, though very constant, was in fact an illusion. When their action was measured and recorded it proved that they really threw the shoulders slightly backward, but alwnys much less than the hips, which were thrown far behind the normal, thus inclining the line of the back forward and giving the illusion of forward shoulders.^[1]

Figure 4 and Figure 5 show the effect of the bad cor­set.^[2]

The forms which we class together as the good corset have equally definite common characteristics and effect on posture. They are all in greater or less degree beneficial to those who suffer from static backache.

The common characteristics of all the forms which we class as good corsets are (1) that they are short behind (especially at the top) and relatively long in front (especially at the bottom); (2) they fit the wearer tightly around the pelvis (especially in the space between the iliac crests and the trochanters) and decrease regu­larly in pressure to their upper edge where they are very loose (especially behind); (3) they arc considerably incurred at the waist line at the back and sides. but show no waist curve in front. Figure 6 is a life sketch of such a corset. The good corsets invariably moved the center of gravity back, and in all our experiments they threw the shoulders back of the normal, but under they effect the hips never moved further backward than did the shoulders and sometimes less. Figure 7 shows the actual effects of the good corsets as recorded.

It will be seen that, though both the bad and good forms of corset move the center of gravity backward in its relation to the base of support (the feet). they affect its relation to the more important bearing points of the body in directly opposite ways, a fact which explains

1. ↑ 5
2. ↑ 6